The Porsche 918 RSR concept is a race-tuned variant of the Porsche 918. It was announced at the 2011 North American International Auto Show in Detroit. In addition to a direct injection 3.4L V8 engine, the 918 RSR concept is equipped with a flywheel-based Kinetic Energy Recovery System (KERS) which provides the power for its two 75kW electric motors, one positioned in the front and one in the rear of the car. The motors each power one front wheel when the driver hits the Boost button. The large flywheel, for storing energy as the car brakes, sits in a vacuum where the passenger seat would usually be in a left-hand drive car.